Stegosaurus' little cousin is found

13 June 2007

A new species of dinosaur, related to the Stegosaurus and Triceratops, has been identified by an international team of scientists including Dr Richard Butler of the Natural History Museum.

The dinosaur, named Eocursor parvus, meaning early little runner, was similar in size to a fox. Unlike many of its large and lumbering later cousins such as Triceratops and as its name suggests, it was a small and agile fast-runner. The new find sheds light on the origins of the plant-eating dinosaurs in the group Ornithischia.

The fossil specimen is the most complete ornithischian fossil to be found in the Triassic period (200- 250 million years ago) and is approximately 220 million years old.

'The few ornithischian fossils from the Triassic are incomplete and controversial, so we know virtually nothing about the group's early evolution,' says Dr Butler.

' Eocursor is enormously important because it helps to fill this gap in the fossil record.'

The Eocursor specimen shows the earliest evidence for the origins of many skeletal characteristics in this group, including the backward-pointing pelvis.

Anatomical comparisons

Dr Butler worked with scientists at the Iziko South African Museum in Cape Town and the University of Cambridge. They compared the anatomy of Eocursor to other ornithischian dinosaurs from all over the world.

The single Eocursor specimen was discovered in 1993 in South Africa's Free State but only recently studied by scientists. It was identified from skull and skeletal material, including the backbone, arms, pelvis and legs.

'Eocursor is a very small and primitive dinosaur that would have eaten plants with its leaf-shaped teeth and had an unusually large, grasping hand.'

'The lower leg bones are very long, suggesting it would have been able to run fast on its hindlegs to escape from predators.'

New evolutionary tree

The scientists were able to produce a new evolutionary tree showing how primitive ornithischians are related to each other. This tree shows that Eocursor is one of the most primitive known ornithischians, and also suggests that ornithischians spread throughout the world later than scientists previously thought.

Butler concludes, 'By placing Eocursor in an evolutionary tree we can begin to understand when and why ornithischian dinosaurs became so important.

It seems that primitive ornithischians were scarce, and the group succeeded by taking advantage of the extinctions of other plant-eating reptiles at the end of Triassic about 200 million years ago.'

The research is published in the journal Proceedings of the Royal Society: Biological Sciences .